Semantic geotokens

ABSTRACT

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for providing geographically relevant search results. In one aspect, a method includes receiving a geotoken for a resource. The geotoken can be a resource token that references a geographic location. A semantic geotoken can be selected using the received geotoken. The semantic geotoken is a standardized representation of the geographic location that includes one or more location-specific terms. The semantic geotoken is stored with a reference to the resource. Neighboring locations for the geographic location are determined. The neighboring locations are within a predetermined distance of the geographic location. Semantic geotokens for the neighboring locations are selected and stored with the reference to the resource. Data specifying the semantic geotokens and the reference to the resource are provided.

BACKGROUND

This document relates to data processing.

The Internet provides access to a wide variety of resources such asvideo or audio files, web pages for particular subjects, book articles,or news articles. A search system can identify resources in response toa text search query that includes one or more search phrases (i.e., oneor more words) or in response to user interactions with anotherinterface. For example, a map interface can include a user interfaceelement that allows a user to input or select search phrases. The searchphrases that are submitted by a user through the map interface caninclude location information from the displayed map area. In response toreceiving search phrases, the search system identifies resources thatare responsive to the search phrases and ranks the resources, forexample, based on their relevance to the search query and on measures ofquality of the resources. In turn, the search system provides searchresults that reference (e.g., link to) the identified resources. Thesearch results are typically ordered for viewing according to the rank.

Some users that provide a search query are interested in receivingsearch results referencing resources that include information relevantto a particular location. For example, a user that submits the searchquery “Atlanta Family Activities” may be searching for web pages thatprovide information about the city of Atlanta. Search results providedin response to the search query “Atlanta Family Activities” may includea web page that does not provide information about family activities inAtlanta, or even the city of Atlanta, but rather merely includes theword Atlanta.

For example, one resource referenced by the search results may be aretailer site that includes a drop-down menu enabling the user tospecify their current location in order to identify retail locationsnear the selected location. Another resource may include the wordAtlanta in a footnote of the resource that specifies a business locationof the company that developed the web page. Although both of theresources described above include the text “Atlanta,” it is unlikelythat these resources would satisfy the informational needs of the userthat submitted the search query for “Atlanta Family Activities” becausethese resources provide very little information about family activitiesin the city of Atlanta.

SUMMARY

In general, one innovative aspect of the subject matter described inthis specification can be embodied in methods that include the actionsof receiving a geotoken for a resource, the geotoken being a resourcetoken that references a geographic location; selecting a semanticgeotoken using the received geotoken, the semantic geotoken being astandardized representation for the geographic location including one ormore location-specific terms for the geographic location; storing thesemantic geotoken with a reference to the resource; determiningneighboring locations for the geographic location, the neighboringlocations being within a predetermined distance of the geographiclocation; selecting semantic geotokens for the neighboring locations;storing the semantic geotokens for the neighboring locations with thereference to the resource; and providing data specifying the semanticgeotokens and the reference to the resource. Other embodiments of thisaspect include corresponding systems, apparatus, and computer programs,configured to perform the actions of the methods, encoded on computerstorage devices.

These and other embodiments can each optionally include one or more ofthe following features. Methods can further include the actions ofreceiving a search query that includes a reference to a geographiclocation that matches at least one of the semantic geotokens for theresource; and providing the resource in response to the request.

Selecting a semantic geotoken comprises selecting a semantic geotokenhaving a confidence score that exceeds a confidence threshold. Selectinga semantic geotoken having a confidence score can include selecting asemantic geotoken in which the confidence score is based, at least inpart, on the distance between the geographic location referenced by thesemantic geotoken and the geographic location specified by the resource.Selecting a semantic geotoken having a confidence score can includeselecting a semantic geotoken in which the confidence score is based, atleast in part, on a position of the geotoken in the resource.

Methods can further include the actions of receiving a search query thatincludes a reference to a geographic location; mapping the reference tothe geographic location to a query semantic geotoken; obtaining searchresults responsive to the search query, at least one obtained searchresult referencing a resource having a semantic geotoken that matchesthe query semantic geotoken; adjusting result scores for the at leastone obtained search result based on the match between the query semanticgeotoken and the semantic geotokens for the at least one obtained searchresult; providing data that cause presentation of the search results ina presentation order that is based on the adjusted result scores.

Providing the data that cause presentation of the search results caninclude providing data that cause presentation of a portion of text fromthe resource that specifies the geographic location referenced by theresource. Receiving the search query that includes a reference to ageographic location can include receiving a search query that includes areference to a geographic location of a user device that submitted thesearch query.

Methods can further include the action of identifying data in theresource that specify the geographic location. Methods can furtherinclude the actions of determining that the geographic locationspecified by the resource is specified with at least a threshold levelof specificity, wherein the threshold level of specificity requires atleast a city and state of the geographic location be specified; and inresponse to the determination, selecting the semantic geotoken for theresource.

Methods can further include the actions of determining that thegeographic location specified on the resource is not specified with atleast a threshold level of specificity; determining that the resourcespecifies less than a threshold number of different geographiclocations; and based on the determinations, selecting the semanticgeotoken for the geographic location referenced by the resource.

Methods can further include the actions of receiving a geographicrelevance score for the geographic location, the geographic relevancescore being a measure of relevance between a resource and a geographiclocation; determining that the geographic relevance score exceeds athreshold level; and in response to the determination, generating ageotoken for the resource.

The semantic geotoken can include location-specific terms, each of theterms separated by a delimiter. The semantic geotoken can include atleast one location-specific term that is not included in the geotoken.The semantic geotoken can include an identifier corresponding togeographic locations stored in a geographic repository. The semanticgeotoken can include a latitude and a longitude of a centroid of thegeographic location.

Particular embodiments of the subject matter described in thisspecification can be implemented so as to realize one or more of thefollowing advantages. The relevance of search results that are providedin response to a search query can be increased by selecting andproviding search results that have been indexed according to semanticgeotokens. The time required to provide search results in response to aquery is reduced by reducing the quantity of “or” clauses that arerequired to be processed by a search system. The quantity of “or”clauses that are required to be processed by a search system are reducedby indexing resources according to semantic geotokens that specify ageographic location to which the resource has been identified asrelevant and semantic geotokens specifying neighboring locations for thegeographic location. The quantity of “or” clauses that are required tobe processed by the search system are reduced by mapping locationphrases of a search query to query semantic geotokens that are used toidentify resources that are responsive to the search query. A searchsystem can provide more relevant search results by adjusting resultscores for resources based on a distance between locations that arereferenced by the resources and a geographic location that is referencedby a location phrase in a search query.

The details of one or more embodiments of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages of thesubject matter will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example environment in which a searchsystem provides search services.

FIG. 2 is a block diagram of example resources that include geotokens.

FIG. 3 is a flowchart of an example process for selecting semanticgeotokens for a resource.

FIG. 4 is a flowchart of an example process for providing search resultsusing semantic geotokens.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

Resources available over the Internet can reference geographic locationsin a variety of ways. For example, one web page can provide informationabout a location at which a particular activity or business is located,while another web page can include a list of geographic locations fromwhich a user can select their particular geographic location. Dataspecifying geographic locations that are referenced by a resource arereferred to as geotokens that associate the resource with the geographiclocation. Analysis of geotokens (e.g., based on the quantity andlocation in the resource of the geotokens) can provide an indication ofwhether a resource is relevant to a particular geographic location, and,in turn, used by a search system to provide relevant search results inresponse to receipt of a search query that includes a location phrase(i.e., one or more terms that specify a geographic location for a searchquery).

Different resources may specify relevant geographic locations indifferent ways. For example, a restaurant web page may list the postoffice address of its location (i.e., an exact street address in a city,such as Atlanta). Meanwhile, a web page that lists local activities fora city may only reference the city name (e.g., Atlanta) withoutproviding exact addresses for the listed activities. Although tworesources may reference the same general geographic location (e.g., thecity of Atlanta), the two resources can use different geotokens tospecify that same general geographic location.

Due to the different geotokens that can be used to reference a samegeographic location, many different alternative location phrases mayneed to be used to identify web pages that are relevant to a particularlocation. For example, if the search query “Family Activities 30309” isreceived, where 30309 is a zip code in Atlanta, a search system may needto rewrite the query to search for “Family Activities (30309 “or”Atlanta or Atlanta, Ga.).” The time required to process a search querygenerally increases in proportion to the number of alternative searchterms (i.e., “or” clauses) that are processed by the search system.Therefore, search results can be provided more quickly by decreasing thenumber of alternative search terms (i.e., “or” clauses) that are addedto a received search query.

Semantic geotokens can be used to reduce the number of alternativesearch terms that are used to locate resources. A semantic geotoken is astandardized expression that represents one or more location-specificterms for a geographic location. For example, resources that referenceAtlanta, Ga. can be indexed to the semantic geotokens “atlanta_ga_us;30309_us; 30312_us; 30313_us . . . ,” such that the resources can beidentified in response to either the search query “Family ActivitiesAtlanta,” or the search query “Family Activities 30309,” withoutincluding alternative location phrases in the search query.

As resources are being indexed, neighboring geographic locations canalso be associated with the resources. For example, a web page for arestaurant in Atlanta can be associated with neighboring towns orsuburbs, such as Decatur, Ga., that are within a threshold distance ofAtlanta. In this example, the restaurant can be associated with all ofthe semantic geotokens that reference the city of Atlanta expressedabove, as well as references to Decatur (e.g., decatur_ga_us; 30034_us;30035_us; . . . ” Thus, the restaurant's web page can be identified aspotentially relevant to a search query for “Restaurants Decatur” asdescribed in more detail below.

FIG. 1 is a block diagram of an example environment 100 in which asearch system 110 provides search services. The example environment 100includes a network 102, e.g., a local area network (LAN), wide areanetwork (WAN), the Internet, or a combination of them, connects websites 104, user devices 106, and the search system 110. The environment100 may include many thousands web sites 104 and user devices 106.

A web site 104 is one or more resources 108 associated with a domainname and hosted by one or more servers. An example web site is acollection of web pages formatted in hypertext markup language (HTML)that can contain text, images, multimedia content, and programmingelements, e.g., scripts. Each web site 104 is maintained by a publisher,e.g., an entity that manages and/or owns the web site.

A resource 108 is any data that can be provided by the web site 104 overthe network 102 and that is associated with a resource address.Resources 108 include HTML pages, word processing documents, portabledocument format (PDF) documents, images, video, and feed sources, toname just a few. The resources can include content, e.g., words,phrases, images and sounds and may include embedded information (e.g.,meta information and hyperlinks) and/or embedded instructions (e.g.,JavaScript scripts).

A user device 106 is an electronic device that is under control of auser and is capable of requesting and receiving resources over thenetwork 102. Example user devices 106 include personal computers, mobilecommunication devices, and other devices that can send and receive dataover the network 102. A user device 106 typically includes a userapplication, e.g., a web browser, to facilitate the sending andreceiving of data over the network 102.

To facilitate searching of resources 108, the search system 110identifies the resources 108 by crawling and indexing the resources 108.Data about the resources 108 can be indexed based on the resource 108 towhich the data corresponds. The indexed and, optionally, cached copiesof the resources 108 are stored in a search index 112.

The user devices 106 submit search queries 114 to the search system 110.In response, the search system 110 accesses the search index 112 toidentify resources 108 that are predicted to be relevant to the searchquery 114, for example based on relevance scores that have been computedfor the resources 108. The search system 110 selects resources 108,generates search results 116 that identify the resources 108, andreturns the search results 116 to the user devices 106. A search result116 is data generated by the search system 110 that references aresource 108 that is responsive to a particular search query, andincludes an active link (e.g., a URL) to the resource. An example searchresult 116 can include a web page title, a snippet of text or a portionof an image extracted from the web page, and the URL of the web page.

User devices 106 receive the search results 116 and render the searchresults 116, for example, in the form of one or more web pages, forpresentation to users. In response to the user selecting a link (e.g.,URL) in a search result at a user device 106, the user device 106requests the resource 108 referenced by the link. The web site 104hosting the resource 108 receives the request for the resource 108 fromthe user device 106 and provides the resource 108 to the requesting userdevice 106.

Search results 116 are selected to be provided to a user device 106 inresponse to a search query 114 based on result scores. Result scores arescores that represent a measure of relevance of the resource 108 to asearch query. For example, a result score for a resource 108 can becomputed based on an information retrieval (“IR”) score corresponding tothe resource 108, and, optionally, a quality score of the resource 108relative to other available resources. A presentation order for thesearch results 116 can be selected according to and/or using the resultscores. In turn, data that cause presentation of the search results 116according to the presentation order can be provided to the user device106.

The search system 110 includes, or is in data communication with, asemantic geotoken apparatus 126 that generates semantic geotokens forresources. As described in more detail below, the semantic geotokens areused to identify resources that are considered relevant to a locationphrase that is included in (or inferred from) a search query. Thesemantic geotoken apparatus 126 is a data processing apparatus includingone or more processors that are configured to generate semanticgeotokens for resources based on one or more references to geographiclocations that are associated with the resource (e.g., text identifyinga geographic location). A geographic reference is associated with aresource by being included in the resource and/or being included in areference (e.g., an active link) to the resource. These geographicreferences are referred to as geotokens.

The semantic geotoken apparatus 126 can generate semantic geotokens forany geographic location, and store the semantic geotoken in a mappingtable. The semantic geotoken for a particular location can include a setof location-specific terms (e.g., city names, zip codes, or stateabbreviations) that reference the geographic location. For example, asemantic geotoken for the city of Atlanta can include the word “atlanta”and the state abbreviation “ga.” The semantic geotoken can includedelimiters between the location-specific terms, such as underscores orother delimiters. For example, the semantic geotoken for Atlanta can be“atlanta_ga_us.” Alternatively, a repository of geographic informationcan be used, with a repository identifier for the correspondinglocation, such as an integer. In some implementations, a latitude andlongitude of a centroid of the city or zip code can be used to representthe city or zip code.

The semantic geotoken apparatus 126 can also generate, for a particularlocation, semantic geotokens for neighboring locations. A neighboringlocation for a particular geographic location is another geographiclocation that is within a predetermined distance of the particulargeographic location. For example, the neighboring locations for Atlantamay be pre-specified to include any city or town (or other specifiedgeographic location) that is located within 10 miles of the centroid ofAtlanta. For example, semantic geotokens for the cities of Decaturand/or Avondale Estates, which are both within 10 miles of the centroidof Atlanta can also be generated and associated with the resource asrelevant to the resource.

The semantic geotoken apparatus 126 analyzes resources, as described inmore detail below, to identify geotokens for the resource. In responseto determining that a resource includes a geotoken for a particularlocation, the semantic geotoken apparatus 126 can select a semanticgeotoken that is associated with the geotoken, and index the resourceaccording to the semantic geotoken, the semantic geotokens ofneighboring locations, and/or overlapping locations (e.g., anoverlapping location can be a location designated by a zip code, whichis also inside a city). For example, a web page that includes thegeotoken “Atlanta,” but does not include a reference to a zip code canalso be indexed with the semantic geotoken that references 30309, suchthat the resource can be identified as relevant to a search query thatincludes the location phrase “30309.”

In some implementations, the semantic geotoken apparatus 126 selectivelydetermines which semantic geotokens to assign to a resource based ongeographic relevance scores for geotokens from a resource. A geographicrelevance score is a value specifying a likelihood that a resource isrelevant to a geographic location that is referenced by a geotoken. Asdescribed in more detail below, the semantic geotoken apparatus 126determines an “on-page” geographic relevance score for a resource 108.An “on page” geographic relevance score is a value specifying a measureof geographic relevance for a resource based on the geotokens that areincluded in the resource itself. The “on page” geographic relevancescore can be determined based on a quantity, placement, and/orspecificity of the geotokens (e.g., words, phrases, meta information,images, audio or other information specifying a geographic location)that are included in the resource 108. For example, a web page thatincludes the text “Atlanta, Ga.” as a tag for the web page can have ahigher on-page geographic relevance score for the location Atlanta thana web page that only includes the text “Atlanta” in a dropdown menu orother “boilerplate” content (e.g., content that is included in manydifferent web pages independent of the topic to which the content isrelevant).

In some implementations, the semantic geotoken apparatus 126 determinesa confidence score for a semantic geotoken for a resource. Theconfidence score is a value indicating a likelihood that the resource isrelevant to the location that is referenced by the semantic geotoken. Insome implementations, the confidence score for a semantic geotoken for aresource is a function of the highest geographic relevance score that isassociated with a geotoken that references the same geographic locationas the semantic geotoken. For example, if a web page references Atlantamultiple times, the web page includes multiple geotokens that eachreference Atlanta, and each of these geotokens can have a differentgeographic relevance score. The semantic geotoken that is generated fromthe “Atlanta” geotokens can have a confidence score that is based on thehighest relevance score among the “Atlanta” geotokens. In someimplementations, the confidence score is a function of all (or a propersubset) of the geographic relevance scores that are associated withgeotokens that reference the same geographic location.

The semantic geotoken apparatus 126 can also compute an “off-page”geographic relevance score. The “off page” geographic relevance score isvalue specifying a measure of geographic relevance for a resource basedon geotokens that are included in references to the resource (i.e.,off-page geotokens), rather than, geotokens on the resource itself. Forexample, the semantic geotoken apparatus 126 can use a quantity ofactive links that link to a web page and that include the anchor text“Atlanta” (or other references to Atlanta, such as zip codes forAtlanta) to determine an off-page geographic relevance score for theresource relative to the location Atlanta. Thus, a web page that is moreoften referenced by active links having anchor text referencing“Atlanta” can have a higher “Atlanta” off-page geographic relevancescore than another web page that is less often referenced by activelinks having anchor text referencing “Atlanta.” In some implementations,the confidence score for the semantic geotoken for a resource is set toa highest off-page geographic relevance score that is associated with asingle off-page geotoken that references the geographic location. Insome implementations, the confidence score is a function of all (or aproper subset of) geographic relevance scores that are associated withoff-page geotokens that reference the resource.

In some implementations, the semantic geotoken apparatus 126 can computethe confidence score of a semantic geotoken for a resource as a functionof the on-page and off-page geographic relevance scores for thegeotokens for the resource. For example, the confidence score for asemantic geotoken for a resource relative to a particular location canbe a sum, product, or a value based on another function of the on-pageand off-page geographic relevance scores that were determined for theresource using the geotokens that reference the particular location.

The semantic geotoken apparatus 126 can store the semantic geotoken forthe resource 108 in the search index 112. Each semantic geotoken that isstored in the search index can be stored in association with (i.e.,indexed according to and/or stored with a reference to) the resource forwhich the semantic geotoken was selected. Each semantic geotoken canalso be stored in association with the confidence score for the semanticgeotoken. The search system 110 can use the semantic geotokens andconfidence scores to compute and/or adjust result scores for resources,as described in more detail below. For example, the result score may becomputed as a dot product, or another function, of the informationretrieval score, the quality score, and/or a confidence score for thesemantic geotoken for the resource.

In some implementations, the semantic geotoken apparatus 126 does notassociate (i.e., index the resource according to and/or store theresource with a reference to) a particular semantic geotoken (i.e., asemantic geotoken that references a particular location) with a resourcewhen the confidence score for the particular semantic geotoken thatfails to exceed a minimum confidence threshold. For example, thesemantic geotoken apparatus 126 can compare the confidence score for asemantic geotoken for a resource to the confidence threshold, and storethe particular semantic geotoken and corresponding confidence score onlywhen the confidence score exceeds the confidence threshold. Thus, theresources that are assigned a particular semantic geotoken can belimited to those resources that are considered to be relevant to thegeographic location referenced by the particular semantic geotoken withat least a minimum specified confidence level.

FIG. 2 is a block diagram of example resources 200 that includegeotokens. In some implementations, the resources 200 are web pages (orother online documents) that have been indexed by a search system. Acomputer system such as the semantic geotoken apparatus 126 examinestokens that have been indexed for (or are included in) resource 202 thatincludes content describing state parks in Pennsylvania. Tokens thatinclude a full or partial reference to a geographic location can beidentified as geotokens. For example, the resource 202 includesgeotokens 204-214 (e.g., tokens referencing Pennsylvania, Erie,Cleveland, and other geographic locations).

The locations of the geotokens in the resource 202 are also identifiedby the computer system. In some implementations, the relevance ofgeotokens can be determined based, in part, on the locations of thegeotokens in the resource 202. Different resource areas (e.g., title,main text, and tags) may be given different weights in a formula todetermine the measures of relevance for the geotokens and, in turn,geographic relevance scores for the geotokens in the resource 202.

For example, the geotoken 204 is included in the title of the resource202, and therefore, may be considered more influential for determining ageographic location to which the resource 202 is relevant than thegeotoken 214 that is located in a footnote of the resource 202. In thisexample, the geotoken 204 may be assigned a higher “weight” fordetermining the relevance of the resource (i.e., relative to geographiclocations) than the weight assigned to geotoken 214. Thus, geotoken 204will be more influential than geotoken 214 for determining measures ofrelevance between the resource and particular geographic locations.

In some implementations, the weight assigned to a geotoken that appearsin the title can be inversely proportional to a quantity of geographiclocations that are referenced by geotokens in the title. If a singlegeographic location is referenced by a geotoken in a resource title, theweight assigned to the geotoken may be higher than the weight assignedto geotokens that respectively reference two or more differentgeographic locations. For example, when a single location is referencedby the title of the resource 202, it is more likely that the resource isrelevant to the geographic location referenced by the geotoken than whenmultiple geotokens referencing multiple different locations are in thetitle.

Geotokens that are located near a beginning of a resource (e.g., withina threshold quantity of words of an article or within a thresholdquantity of pixels of a top of the web page) are referred to as “leadinggeotokens” and may provide a reliable indication of the locations towhich the resource 202 is relevant. Therefore, leading geotokens may beassigned a higher weight than geotokens that appear later in theresource (e.g., outside of the threshold quantity of words or outside ofthe threshold quantity of pixels).

For example, the geotoken 206 is in the first sentence of the firstparagraph of the resource 202, and therefore, may be assigned a higherweight than the geotoken 208 that is included in the second paragraph ofthe resource 202. In another example, a news article might have a bylinethat includes a geotoken representing the location where the newsarticle was filed and/or written. This geotoken may be assigned a higherweight than geotokens that appear later in the article because thelocation listed in the byline is often the location where eventsreported in the news article occurred. Therefore, this geotoken may be areliable indication of a geographic location to which the news articleis relevant.

Some resources (e.g., web pages) include tags, which may be presented tothe user, as shown in the resource, or stored in meta information forthe resource. These tags are often used by a resource author tofacilitate indexing and discovery of a resource. Therefore, geotokensthat are included in tags can be a reliable indicator of a location towhich the resource is relevant. Accordingly, a geotoken that appears ina tag may be assigned a higher weight than a geotoken that appears inthe body of an article. For example, the geotoken 212 is included in atag of the resource 202 to indicate that the resource 202 is related toErie County, Pennsylvania. Thus, the geotoken 212 may be assigned ahigher weight than geotoken 210 because geotoken 210 was not identified,for example, as a leading geotoken, or otherwise determined to beassigned an increased weight.

Geotokens that are located in some portions of a resource can beeliminated or be assigned lower weights than other geotokens in theresource. For example, geotokens that are included in “boilerplate”content can be ignored, or be assigned a weight that is lower than theweights assigned to other geotokens in the resource. As noted above,boilerplate is content that is included in many different web pagesindependent of the topic to which the content is relevant. Exampleboilerplate includes document elements such as headers, footers,drop-down menus, and legal disclaimers. Boilerplate may be included in aresource to aid user navigation of the resource, to provide a consistentlook and feel across web pages in a website, or may be the result ofusing a template to generate the resource. For example, the token 214provides a location of the web developer that created the resource 202in a footer of the resource 202. Therefore, the geotoken 214 can beidentified as boilerplate since it is located in the footer of theresource 202.

Qualified geotokens can be assigned a higher weight than unqualifiedgeotokens. Qualified geotokens are geotokens that are formed by themerger of two individual geotokens. For example, Cleveland and Ohio areboth geotokens that when combined create the qualified geotoken“Cleveland, Ohio” (e.g., geotoken 214). The geotoken 214 is morespecific than unqualified geotokens, such as the geotoken 210, whichincludes Cleveland, but does not include Ohio. Qualified geotokensgenerally include individual geotokens that are located adjacent to eachother and/or appear in a specified sequence, but can be created fromgeotokens that are not adjacent to each other or in a specifiedsequence. For example, if Springfield and Ohio both appear on the pageand no other states containing Springfield (e.g., Missouri or Illinois)appear on the page, then the geotokens Springfield and Ohio can bereliably combined to make the terms Springfield and Ohio less ambiguous.

Qualified geotokens may be more reliable indicators of a geographiclocation to which the geotoken is referring. For example, theunqualified geotoken “Cleveland” in isolation could be referring to oneof at least twenty six cities, towns, or other municipalities in Americathat are named Cleveland. However, when “Cleveland” is qualified by(e.g., appears with) “Ohio,” the location being referred to is lessambiguous. In some implementations, semantic geotokens are only selectedfor a resource when the geotoken has at least a threshold specificity.In these implementations, the geotoken can be required to be a qualifiedgeotoken or otherwise refer to a geographic location with a minimumlevel of specificity. For example, the geotoken can be required toreference at least a city and state, and the references to the city andstate can be required to be within a specified number of pixels of eachother. Additionally, the geotoken can be required to reference a streetaddress, and this reference to the street address can be required to bewithin a specified number of pixels of the references to the city and/orstate.

Other resources, such as resources 216-220 can include references222-226 (e.g., hypertext links) to the resource 200. Each of thereferences 222-226 includes a geotoken. For example, reference 222includes the geotoken Pennsylvania, while reference 226 includes thegeotoken Erie County. Inclusion of a geotoken in a reference to a targetresource (e.g., resource 202) is an indication that the target resourceis relevant to the location specified by the geotoken. Therefore,geotokens that reference a target resource can be used when computingthe off-page geographic relevance score for the geotokens for the targetresource. For example, when a large portion of references to the targetresource include geotokens that reference a same geographic location, itis likely that the target resource is relevant to the referencedgeographic location.

FIG. 3 is a flowchart of an example process 300 for selecting semanticgeotokens for a resource. The process 300 is a process by whichgeotokens for a resource are received and a semantic geotoken isselected for a geographic location that is specified by the geotokens. Aset of locations are selected as neighboring locations for thegeographic location. Semantic geotokens are then generated for each ofthe neighboring locations for the geographic location, and data thatspecify the semantic geotokens and a reference to the resource arestored and provided.

The process 300 can be implemented, for example, by the semanticgeotoken apparatus 126 and/or the search system 110 of FIG. 1. In someimplementations, the semantic geotoken apparatus 126 is a dataprocessing apparatus that includes one or more processors that areconfigured to perform actions of the process 300. In someimplementations, a computer readable medium can include instructionsthat when executed by a computer cause the computer to perform actionsof the process 300.

Geotokens for a resource are received (302). In some implementations,each geotoken is a resource token (i.e., a word, set of words, audiofile, video file, or other unit of content) that references a geographiclocation. Each geotoken can be identified from a set of resource tokensthat have been indexed for the resource, for example, in a data storethat stores data for the resource (e.g., the search index 112 of FIG.1). The geotokens can be identified from a set of tokens that are storedwith a reference to an index number and data type such that the resourcecan be represented by a string of tokens that have been extracted fromthe resource. For example, the tokens can be compared to a data set ofknown geographic locations. Tokens that match or substantially match aknown geographic location (e.g., tokens that are stubs, synonyms, commonmisspellings, alternative names for known geographic locations, orotherwise identified to represent known locations) are identified asgeotokens for the resource.

A token may also be examined in the context of surrounding tokens todetermine if the token is used as a geotoken. For example, a number,followed by a proper noun, followed by a type of street or streetabbreviation may be identified as a street address and marked as ageotoken. Adjacent geotokens may be identified and combined to create aqualified geotoken. For example, the text “Erie, Pa.” can be treated asa single qualified geotoken, as described with reference to FIG. 2.

A geographic relevance score can be computed for each geotoken received.The geographic relevance score can be based on the resolution of thegeotoken, i.e., how precise a geographic location the geotokenreferences. For example, a geotoken that includes a full postal streetaddress is a more precise geotoken than another geotoken that includesonly a reference to a city. In some implementations, the geographicrelevance scores for geotokens that are more precise are higher than thegeographic relevance scores for less precise geotokens.

The geographic relevance score for each geotoken can also be based on aresource location (i.e., a location of the geotoken in the resource) ofthe geotoken. In some implementations, the resource location isspecified by token attribute values. The token attribute values can alsospecify characteristics of the tokens. For example, in addition tospecifying a location of the geotoken in a resource, the token attributevalues can specify whether the geotoken is included in a tag for theresource or whether the geotoken is included in boilerplate content. Thegeotoken attribute values can also specify whether the geotoken ishighlighted, bolded, or otherwise visually emphasized relative to othercontent that is presented with the resource. The geotoken attributevalues can further specify whether the geotoken is included in a titleof the resource or whether the geotoken is a merger of two or moretokens. In some implementations, when a geotoken is identified as beingincluded in boilerplate, that geotoken can be removed from the geotokensthat have been identified for the resource.

In some implementations, portions of resources that are considered areasof high importance (e.g., for determining relevance of a resource to aparticular location) may be pre-defined, and geotokens that fall withinthose areas may be assigned higher geographic relevance scores thanother geotokens. For example, portions of a resource that contain anoverview, summary, or which—according to resource authoringconvention—are indicative of locations to which the resource is relevantmay be identified as areas in which geographic relevance score isincreased relative to other geotokens. Examples of these high importanceareas include a resource title, tag, and opening content (i.e., leadingmentions). Geotokens that are considered to be in areas that are lessindicative of the relevancy of the resource to a geographic location(e.g., boilerplate content) may be assigned a reduced geographicrelevance score relative to other content, or be assigned a geographicrelevance score of 0.

In some implementations, the geotokens for a particular resource can begeotokens for other resources that belong to the same web site or domainas the particular resource. For example, a restaurant can have a websitewith a “home” page resource and a separate “contact” page resource. Thecontact page can list the address of the restaurant, which can beidentified as a geotoken for the contact page. The geotoken referencingthe address of the restaurant can also be used as a geotoken for thehome page resource, as the geotoken is likely to be relevant to the homepage of the restaurant website.

A semantic geotoken is selected using the received geotoken (304). Thesemantic geotoken can be a standardized representation of the geographiclocation that is referenced by the geotoken. The semantic geotokens canbe selected, for example, from a data store that stores semanticgeotokens that are indexed by the geographic location for which thesemantic geotoken was created.

In some implementations, a semantic geotoken can be selected for aresource that includes a single high-precision geotoken (i.e., ageotoken having a precision that exceeds a precision threshold). Forexample, the precision threshold can require inclusion of a streetaddress, rather than just a mention of a city. Another precisionthreshold can require references to a zip code, as opposed to an entirecity. If there are multiple precise geographic locations referenced on aresource, multiple geotokens and multiple semantic geotokens can begenerated for each geographic location.

In some implementations, semantic geotokens are selected for resourcesthat include low-precision geotokens (i.e., geotokens having a precisionthat does not exceed the precision threshold) if there are fewer than athreshold quantity of different geographic locations referenced. Forexample, in some implementations, the semantic geotoken apparatus 126determines that a particular geographic location specified by a resourceis not specified with at least the threshold precision. In response tothis determination, the sematic geotoken apparatus 126 determineswhether the resource specifies a threshold number of differentgeographic locations. If the resource does not specify at least thethreshold number of different geographic locations, a semantic geotokencan be selected for the particular geographic location. If the resourcedoes specify at least the threshold number of different geographiclocations, a semantic geotoken will not be selected for the particulargeographic location.

The precision of a particular geotoken relates to a specificity withwhich a particular geographic location is referenced. For example, ageotoken that specifies a street address is more precise than a geotokenthat specifies only a city and/or state. As described above, aconfidence score is a value indicating a likelihood that a particularresource is relevant to a particular geographic location. The confidencescore can be computed based on the precision of the geotokens that areincluded in the resource, the locations of the geotokens in theresource, and other factors (e.g., the number of geotokens thatreference the particular location and/or a number of differentgeographic locations referenced by the resource.) As noted above, asingle high-precision geotoken can provide sufficient confidence that aresource is relevant to a particular geographic location, while multiplelower-precision geotokens may be required to provide sufficientconfidence of relevance to a geographic location.

In some implementations, the semantic geotoken can includelocation-specific terms that each references the geographic locationthat is referenced by the semantic geotoken. For example, a web page fora restaurant can list “555 Example St., Atlanta, Ga., 30303,” as theaddress of the restaurant. As described above, this address can beidentified as a high-precision geotoken, such that the inclusion of thisgeotoken alone provides sufficient confidence that the resource isrelevant to the location Atlanta, Ga. Therefore, “Atlanta, Ga.” and thezip code “30303” can be selected as geotokens for which semanticgeotokens are associated with the web page in this example.

The semantic geotoken for “Atlanta, Ga.” can be expressed as“atlanta_ga_us.” The semantic geotoken includes underscore delimitedreferences to the location-specific terms, “atlanta,” “ga,” and “us,”referring to the city, state, and country, respectively. The semanticgeotoken for zip code “30303” can be expressed as “30303_us,” whichincludes the location-specific terms “30303” and “us.” In someimplementations, the semantic geotokens are standardized to“[city]_[state]_[country]” and/or “[zip (or postal) code]_[country].”The semantic geotokens can include location-specific terms that are notincluded in the geotoken. For example, the country information is notincluded in “Atlanta, Ga.,” but the semantic geotoken can include thecountry information in the location-specific term “us.” The semanticgeotokens can also include information regarding the resolution of thegeotoken that was included in the resource. For example, when theexample address above is used to select the semantic geotokens“atlanta_ga_us” and “30303_us,” the semantic geotokens that areassociated with the resource can include an indicator, such as“STREET_LEVEL,” to indicate that the original resolution of the geotokenwas a street level address. In some implementations, semantic geotokensthat are selected to express a geographic location can include moreprecise location-specific terms or less precise location-specific termsthan those provided in the examples above. In some implementations,multiple resolutions can be used for indexing. For example, a semanticgeotoken for the state, region, or country can be indexed as well. Insome implementations, the semantic geotokens can be translated to acoordinate system or some other system that provides standardidentifiers to geographic locations. For example, semantic geotokens canbe translated to longitudinal and latitudinal coordinates. In someimplementations, integers or some other synthetic identifier associatedwith a repository of geographic information can be used.

In some implementations, geotokens for the same resource and thatreference the same geographic location can be grouped as one geotoken.The semantic geotoken for a group of geotokens can use the highestgeographic relevance score among the group of geotokens that referencethe same geographic location. In some implementations, a separatesemantic geotoken can be generated for each received geotoken,regardless of whether the received geotokens refer to the samegeographic location or not. In some implementations, having separatesemantic geotokens for each geotoken on the resource can allow thesearch system to provide snippets of information or text with thesemantic geotoken and the reference to the resource in a search result.The snippet of information can include text from the resource thatincludes the geographic location. The snippet of information can providethe context of the reference to the geographic location from which thegeotoken was generated. In some implementations, a semantic geotoken isselected from geotokens with geographic relevance scores that exceed athreshold geographic relevance score.

The semantic geotokens are stored with a reference to the resource(306). The reference to the resource can be a network location (e.g., auniform resource identifier) for the resource or another reference thatuniquely identifies the resource. The reference can be stored with allthe semantic geotokens that were selected using the geotokens for theresource. The confidence scores of each of the semantic geotokens can bestored with the semantic geotokens. In some implementations, eachsemantic geotoken generated is stored with a separate reference to theresource, for example, as semantic geotoken-reference pairs (e.g.,Resource_URL:Semantic_Geotoken_(—)1; Resource_URL:Semantic_Geotoken_(—)2or Semantic_Geotoken_(—)1:Resource_URL;Semantic_Geotoken_(—)2:Resource_URL). In some implementations, all thesemantic geotokens are stored together with the reference to theresource (e.g.,Resource_URL:Semantic_Geotoken_(—)1:Semantic_Geotoken_(—)2). Thesemantic geotokens and the reference to the resource can be stored withcorresponding confidence scores in the search index 112 of FIG. 1.

Neighboring locations for the geographic location of the geotokens aredetermined (308). Neighboring locations are geographic locations havingcentroids that are less than a threshold distance away from the centroidof the geographic location referenced by the geotoken. For example, witha threshold distance of 10 kilometers, the city of Raritan, N.J. may beconsidered a neighboring location for a restaurant in Somerville, N.J.In some implementations, the neighboring locations include the citiesand zip codes within the threshold distance. Neighboring locations canbe determined for providing geographically relevant search results. Forexample, a user looking for pizza in Somerville may be willing to travelto Raritan, or to other restaurants, within a reasonable distance.

Semantic geotokens are selected for the neighboring locations (310). Thesemantic geotokens for the neighboring locations can be selected in amanner similar to the semantic geotokens of the referenced geographiclocations. The confidence score of neighboring semantic geotokens can beadjusted based on the distance between the neighboring location and thereferenced geographic location. In some implementations, confidencescores for neighboring locations can be lowered in proportion to thedistance of the neighboring locations to the referenced geographiclocation. For example, the semantic geotoken “somerville_nj_us” can beused to select neighboring semantic geotokens including, “<08807_us,0.0>,” “<08869_us, 0.0>,” “<08896_us, 1.98>,” “<raritan_nj_us, 3.04>,”where the number indicates the distance in kilometers. The first twosemantic geotokens have distances of “0.0” as the two zip codes overlapwith Somerville, N.J. These distances can be factored into theconfidence score of the semantic geotoken. Thus, the confidence scorefor the neighboring semantic geotoken can be a function of thegeographic relevance score of the underlying geotoken (which wouldreference Somerville, N.J., in this example), adjusted by the distance.

Lowering the confidence score based on distance can result in resourcesthat reference neighboring locations that are further away beingreferenced lower in search results than equally relevant resources thatreference closer neighboring locations. For example, for a usersearching for pizza restaurants in Somerville, a resource referencing apizza restaurant in Raritan may be relevant to the search query, but toa lesser extent than resources referencing pizza restaurants inSomerville.

The semantic geotokens for the neighboring locations are also storedwith a reference to the resource (312). The semantic geotokens for theneighboring locations can be stored with the reference to the resourcein a manner similar to the semantic geotokens from the resource. Theneighboring semantic geotokens can be stored with correspondingconfidence scores in separate semantic geotoken-reference pairs, or withthe semantic geotokens from the resource.

Data specifying the semantic geotokens and the reference to the resourceare provided (314). In some implementations, the data are provided to asearch system that uses the data to service search queries that specifya geographic location. In some implementations, the data are stored andindexed according to the resource.

FIG. 4 is a flowchart of an example process 400 for providing searchresults using semantic geotokens. The process 400 is a process by whicha set of search results having semantic geotokens that match a locationphrase of a search query are selected. In turn, result scores for theselected search results are adjusted based on confidence scores for thesemantic geotokens. Data that cause presentation of the search resultsaccording to the adjusted result scores are then provided. In someimplementations, the adjustment of the result scores results in areordering of the search results for presentation. For example, a searchresult that is most relevant to a geographic location specified by thequery (e.g., according to the semantic geotoken confidence scores) canbe promoted (e.g., assigned a higher page presentation position)following adjustment of the result scores, while a search result that isless relevant may be demoted (e.g., assigned a lower page presentationposition) following adjustment of the result scores.

The process 400 can be implemented, for example, by the semanticgeotoken apparatus 126 and/or the search system 110 of FIG. 1. In someimplementations, the semantic geotoken apparatus 126 is a dataprocessing apparatus that includes one or more processors that areconfigured to perform actions of the process 400. In otherimplementations, a computer readable medium can include instructionsthat when executed by a computer cause the computer to perform actionsof the process 400.

A search query that includes a reference to a geographic location isreceived (402). In some implementations, the query includes a locationphrase (i.e., one or more terms that specify a geographic location for asearch query). A location phrase can be a city name, a zip code, alatitude/longitude coordinate pair, or another geographic identifier.

Location phrases can match a geographic identifier for a particulargeographic location by having a geographic identifier that includes anyreference to the particular geographic region (e.g., zip code) orincludes a reference to a location that is within a specified distanceof a the particular geographic region. For example, if the particulargeographic location includes the city of San Francisco and all areaswithin 50 miles of the center of San Francisco, then geographicidentifiers for queries that reference the city of San Francisco (e.g.,zip code 94131), or locations within 50 miles of the city of SanFrancisco, (e.g., Oakland, Calif.), will match the geographic identifierfor the San Francisco region.

In some implementations, the location phrase can be determined and/orinferred based on a location of a user device that submitted the searchquery. The location of the user device can be detected based on userdevice data that is provided with the search query. For example, a userlocation associated with a particular search query can be detected usinguser profile data provided by the user and/or an anonymized InternetProtocol (IP) address (e.g., a hash value computed using the IP address)corresponding to the user device. When the user device is a mobiledevice (e.g., cell phone, Personal Data Assistant, smart phone, or otherportable data communications device) the user location can also beprovided by location-based services (e.g., GPS) that have been enabledby the user.

The reference to the geographic location is mapped to a query semanticgeotoken (404). A query semantic geotoken is a semantic geotoken that isselected (e.g., by the apparatus 126 of FIG. 1) for a search query thatincludes a reference to a geographic location. The query semanticgeotoken is used to identify search results that have a semanticgeotoken that matches the query semantic geotoken.

Mapping the reference to the geographic location to a query semanticgeotoken can be accomplished in a manner similar to producing geotokensfrom references to geographic locations on a resource. For example, if auser inputs a search query, “Chicago weather,” the term “Chicago” can bedetermined to be a reference to a geographic location and mapped to thesemantic geotoken “chicago_il_us.” The search query can be rewritten toinclude a semantic geotoken, as well as the original search query text.Similarly, the query “Chicago, Ill. USA Weather” can be rewritten sothat the semantic geotoken “chicago_il_us” map to the words “Chicago,”“Illinois,” and “USA” in the query. Thus, even if a resource onlymentioned the word “Chicago,” the resource could be identified asresponsive to the query.

A set of search results responsive to the query are obtained, at leastone search result referencing a resource having a semantic geotoken thatmatches the query semantic geotoken (406). The set of search results caninclude, for example, those search results having a highest N resultscores relative to the search query. The search results andcorresponding result scores can be received, for example, from thesearch system 110 of FIG. 1. As described with reference to FIG. 1, theresult scores can be determined by the search system 110, for example,based on IR scores for resources referenced by the search results and/orquality measures for the resources. The result scores can be used, forexample, to select an initial or default ranking for the search results.

The result scores are adjusted for the at least one obtained searchresult based on the match between the query semantic geotoken and thesemantic geotokens for the at least one obtained search result (408). Insome implementations, the confidence scores of the semantic geotokensare used to adjust the result scores for search results that are matchedby the query semantic geotoken. The result scores can be adjusted, forexample, by computing a sum, product, or another function (e.g., alogarithmic function) of the result scores and the confidence scores ofthe matched semantic geotokens.

Data that cause presentation of the search results according to theadjusted result scores are provided (410). The data can be provided inresponse to receipt of the search query. For example, the data canspecify a list of search results and a relative (or absolute)presentation position for each of the search results. The data can bepackaged into a data format for transmission to the user device thatsubmitted the search request previously. For example, the search resultscan be included in a web page or application message, which may alsooptionally include navigation elements, control elements to modify thesearch query, links to additional or sponsored resources, graphics, andappropriate meta information, to name a few.

The description above describes selecting resources that have beenpre-indexed to semantic geotokens in response to a search query thatincludes a location phrase. In some implementations, the location phrasemay be inferred based on a geographic location of the user, as describedabove. In these implementations, the search results that are selectedcan include search results for resources that reference geographiclocations that are within a threshold distance of the inferred location.

For example, if the user is using a GPS enabled device to submit asearch query, the user can enable location-based services that enablethe device to provide data specifying the user's location with thesearch query. In this example, the user's location can include the cityand/or zip code, which can be mapped to a query semantic geotoken.Alternatively or in addition, the user's location can be expressed as agrid location on a map representation (or a latitude/longitudecoordinate pair). The map representation can be segmented, for example,into grid portions (e.g., squares), and the grid portion that representsthe users location can be submitted with the search query. Using theuser's location and the size of the grid portions, resources thatreference locations inside (and/or have been indexed to) grid portionsthat are within a threshold distance of user's location can be selectedin response to the search query. In turn, the search results provided tothe user can include the selected search results.

Embodiments of the subject matter and the operations described in thisspecification can be implemented in digital electronic circuitry, or incomputer software, firmware, or hardware, including the structuresdisclosed in this specification and their structural equivalents, or incombinations of one or more of them. Embodiments of the subject matterdescribed in this specification can be implemented as one or morecomputer programs, i.e., one or more modules of computer programinstructions, encoded on computer storage medium for execution by, or tocontrol the operation of, data processing apparatus. Alternatively or inaddition, the program instructions can be encoded on anartificially-generated propagated signal, e.g., a machine-generatedelectrical, optical, or electromagnetic signal, that is generated toencode information for transmission to suitable receiver apparatus forexecution by a data processing apparatus. A computer storage medium canbe, or be included in, a computer-readable storage device, acomputer-readable storage substrate, a random or serial access memoryarray or device, or a combination of one or more of them. Moreover,while a computer storage medium is not a propagated signal, a computerstorage medium can be a source or destination of computer programinstructions encoded in an artificially-generated propagated signal. Thecomputer storage medium can also be, or be included in, one or moreseparate physical components or media (e.g., multiple CDs, disks, orother storage devices).

The operations described in this specification can be implemented asoperations performed by a data processing apparatus on data stored onone or more computer-readable storage devices or received from othersources.

The term “data processing apparatus” encompasses all kinds of apparatus,devices, and machines for processing data, including by way of example aprogrammable processor, a computer, a system on a chip, or multipleones, or combinations, of the foregoing The apparatus can includespecial purpose logic circuitry, e.g., an FPGA (field programmable gatearray) or an ASIC (application-specific integrated circuit). Theapparatus can also include, in addition to hardware, code that createsan execution environment for the computer program in question, e.g.,code that constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, a cross-platform runtimeenvironment, a virtual machine, or a combination of one or more of them.The apparatus and execution environment can realize various differentcomputing model infrastructures, such as web services, distributedcomputing and grid computing infrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub-programs, or portions of code). A computer program can be deployedto be executed on one computer or on multiple computers that are locatedat one site or distributed across multiple sites and interconnected by acommunication network.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform actions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application-specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of a computer area processor for performing actions in accordance with instructions andone or more memory devices for storing instructions and data. Generally,a computer will also include, or be operatively coupled to receive datafrom or transfer data to, or both, one or more mass storage devices forstoring data, e.g., magnetic, magneto-optical disks, or optical disks.However, a computer need not have such devices. Moreover, a computer canbe embedded in another device, e.g., a mobile telephone, a personaldigital assistant (PDA), a mobile audio or video player, a game console,a Global Positioning System (GPS) receiver, or a portable storage device(e.g., a universal serial bus (USB) flash drive), to name just a few.Devices suitable for storing computer program instructions and datainclude all forms of non-volatile memory, media and memory devices,including by way of example semiconductor memory devices, e.g., EPROM,EEPROM, and flash memory devices; magnetic disks, e.g., internal harddisks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROMdisks. The processor and the memory can be supplemented by, orincorporated in, special purpose logic circuitry.

To provide for interaction with a user, embodiments of the subjectmatter described in this specification can be implemented on a computerhaving a display device, e.g., a CRT (cathode ray tube) or LCD (liquidcrystal display) monitor, for displaying information to the user and akeyboard and a pointing device, e.g., a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide for interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input. In addition, a computer can interact with a user bysending documents to and receiving documents from a device that is usedby the user; for example, by sending web pages to a web browser on auser's client device in response to requests received from the webbrowser.

Embodiments of the subject matter described in this specification can beimplemented in a computing system that includes a back-end component,e.g., as a data server, or that includes a middleware component, e.g.,an application server, or that includes a front-end component, e.g., aclient computer having a graphical user interface or a Web browserthrough which a user can interact with an implementation of the subjectmatter described in this specification, or any combination of one ormore such back-end, middleware, or front-end components. The componentsof the system can be interconnected by any form or medium of digitaldata communication, e.g., a communication network. Examples ofcommunication networks include a local area network (“LAN”) and a widearea network (“WAN”), an inter-network (e.g., the Internet), andpeer-to-peer networks (e.g., ad hoc peer-to-peer networks).

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other. In someembodiments, a server transmits data (e.g., an HTML page) to a clientdevice (e.g., for purposes of displaying data to and receiving userinput from a user interacting with the client device). Data generated atthe client device (e.g., a result of the user interaction) can bereceived from the client device at the server.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular embodiments of particular inventions.Certain features that are described in this specification in the contextof separate embodiments can also be implemented in combination in asingle embodiment. Conversely, various features that are described inthe context of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments, and it should beunderstood that the described program components and systems cangenerally be integrated together in a single software product orpackaged into multiple software products.

Thus, particular embodiments of the subject matter have been described.Other embodiments are within the scope of the following claims. In somecases, the actions recited in the claims can be performed in a differentorder and still achieve desirable results. In addition, the processesdepicted in the accompanying figures do not necessarily require theparticular order shown, or sequential order, to achieve desirableresults. In certain implementations, multitasking and parallelprocessing may be advantageous.

What is claimed is:
 1. A method performed by data processing apparatusfor managing geotokens, the method comprising: receiving a geotoken fora resource, the geotoken being a resource token that references ageographic location; selecting a semantic geotoken using the receivedgeotoken for the resource, the semantic geotoken being a standardizedrepresentation for the geographic location, wherein the semanticgeotoken is selected based on a geographic relevance score for thegeotoken for the resource, the geographic relevance score specifying alikelihood that the resource is relevant to the geographic location thatis referenced by the geotoken for the resource; calculating a confidencescore for the semantic geotoken based, at least in part, on a geographicdistance between a referenced geographic location in the semanticgeotoken and the geographic location referenced by the geotoken for theresource; determining, via a processor, that the confidence score forthe semantic geotoken exceeds a confidence threshold; in response to thedetermination, storing the semantic geotoken with a reference to theresource in a search index; determining neighboring locations for thegeographic location, the neighboring locations being within apredetermined distance of the geographic location; selecting semanticgeotokens for the neighboring locations; and storing the semanticgeotokens for the neighboring locations with the reference to theresource in the search index.
 2. The method of claim 1, furthercomprising: receiving a search query that includes a particularreference to a particular geographic location that matches at least oneof the semantic geotokens that is stored in the search index; andproviding a search result referencing a particular resource that isreferenced by a matching semantic geotoken in the search index inresponse to the search query.
 3. The method of claim 1, wherein theconfidence score for the semantic geotoken is further based on a numberof off-page geotokens that are included in resources that reference theresource.
 4. The method of claim 1, wherein the confidence score for thesemantic geotoken is further based, at least in part, on a position ofthe geotoken in the resource.
 5. The method of claim 1, furthercomprising: receiving, from a client device, a search query thatincludes a particular reference to a particular geographic location;mapping the particular reference to the particular geographic locationto a query semantic geotoken; obtaining search results responsive to thesearch query, at least one obtained search result referencing aparticular resource that is referenced by a matching semantic geotokenin the search index that matches the query semantic geotoken; andproviding data that cause presentation of the search results to theclient device.
 6. The method of claim 5, wherein providing the data thatcause presentation of the search results comprises causing presentationof a portion of text from the at least one obtained search result. 7.The method of claim 5, wherein receiving the search query that includesthe particular reference to the particular geographic location comprisesreceiving the search query that includes the particular reference to ageographic location of the client device that submitted the searchquery.
 8. The method of claim 1, further comprising: determining thatthe geotoken that references the geographic location has at least athreshold level of specificity.
 9. The method of claim 1, furthercomprising: determining that the geotoken that references the geographiclocation does not have at least a threshold level of specificity; anddetermining that the resource has fewer than a threshold number ofgeotokens that reference different geographic locations.
 10. The methodof claim 1, wherein the standardized representation for the geographiclocation includes location-specific terms, each of the terms beingseparated by a delimiter.
 11. The method of claim 1, wherein thesemantic geotoken includes at least one location-specific term that isnot included in the geotoken.
 12. The method of claim 1, wherein thesemantic geotoken includes an identifier corresponding to geographiclocations stored in a geographic repository.
 13. The method of claim 1,wherein the semantic geotoken includes a latitude and a longitude of acentroid of the geographic location.
 14. A non-transitory computerstorage medium encoded with a computer program, the program comprisinginstructions that when executed by data processing apparatus cause thedata processing apparatus to perform operations for managing geotokenscomprising: receiving a geotoken for a resource, the geotoken being aresource token that references a geographic location; selecting asemantic geotoken using the received geotoken for the resource, thesemantic geotoken being a standardized representation for the geographiclocation, wherein the semantic geotoken is selected based on ageographic relevance score for the geotoken for the resource, thegeographic relevance score specifying a likelihood that the resource isrelevant to the geographic location that is referenced by the geotokenfor the resource; calculating a confidence score for the semanticgeotoken based, at least in part, on a geographic distance between areferenced geographic location in the semantic geotoken and thegeographic location referenced by the geotoken for the resource;determining that the confidence score for the semantic geotoken exceedsa confidence threshold; in response to the determination, storing thesemantic geotoken with a reference to the resource in a search index;determining neighboring locations for the geographic location, theneighboring locations being within a predetermined distance of thegeographic location; selecting semantic geotokens for the neighboringlocations; and storing the semantic geotokens for the neighboringlocations with the reference to the resource in the search index.
 15. Asystem for managing semantic geotokens comprising: one or more computersoperable to interact with a user device and further operable to performoperations including: receiving a geotoken for a resource, the geotokenbeing a resource token that references a geographic location; selectinga semantic geotoken using the received geotoken for the resource, thesemantic geotoken being a standardized representation for the geographiclocation, wherein the semantic geotoken is selected based on ageographic relevance score for the geotoken for the resource, thegeographic relevance score specifying a likelihood that the resource isrelevant to the geographic location that is referenced by the geotokenfor the resource; calculating a confidence score for the semanticgeotoken based, at least in part, on a geographic distance between areferenced geographic location in the semantic geotoken and thegeographic location referenced by the geotoken for the resource;determining that the confidence score for the semantic geotoken exceedsa confidence threshold; in response to the determination, storing thesemantic geotoken with a reference to the resource in a search index;determining neighboring locations for the geographic location, theneighboring locations being within a predetermined distance of thegeographic location; selecting semantic geotokens for the neighboringlocations; and storing the semantic geotokens for the neighboringlocations with the reference to the resource in the search index. 16.The system of claim 15, wherein the one or more computers comprise oneor more servers operable to interact with the user device through a datacommunication network, and the user device is operable to interact withthe one or more servers as a client.
 17. The system of claim 15, whereinthe one or more computers are further operable to perform operationsincluding: receiving a search query that includes a particular referenceto a particular geographic location that matches at least one of thesemantic geotokens that is stored in the search index; and providing asearch result referencing a particular resource that is referenced by amatching semantic geotoken in the search index in response to the searchquery.
 18. The system of claim 15, wherein the confidence score for thesemantic geotoken is further based on a number of off-page geotokensthat are included in resources that reference the resource.
 19. Thesystem of claim 15, wherein the confidence score for the semanticgeotoken is further based, at least in part, on a position of thegeotoken in the resource.
 20. The system of claim 15, wherein the one ormore computers are further operable to perform operations including:receiving, from a user device, a search query that includes a particularreference to a particular geographic location; mapping the particularreference to the particular geographic location to a query semanticgeotoken; obtaining search results responsive to the search query, atleast one obtained search result referencing a particular resource thatis referenced by a matching semantic geotoken in the search index thatmatches the query semantic geotoken; and adjusting result scores for theat least one obtained search result based on match level between thequery semantic geotoken and the semantic geotokens for the at least oneobtained search result; and providing data that cause presentation ofthe search results to the user device.
 21. The system of claim 20,wherein providing the data that cause presentation of the search resultscomprises causing presentation of a portion of text from the at leastone obtained search result.
 22. The system of claim 20, whereinreceiving the search query that includes the particular reference to theparticular geographic location comprises receiving the search query thatincludes the particular reference to a geographic location of the userdevice that submitted the search query.
 23. The system of claim 15,wherein the one or more computers are further operable to performoperations including: determining that the geotoken that references thegeographic location has at least a threshold level of specificity. 24.The system of claim 15, wherein the one or more computers are furtheroperable to perform operations including: determining that the geotokenthat references the geographic location does not have at least athreshold level of specificity; and determining that the resource hasfewer than a threshold number of different geographic locations.